symmetal

I use SGP and it overlays a best fit curve over the autofocus V curve, so tends to ignore the odd sample outside the norm. You need fairly steep sides to the V curve too for it to work well, set by your autofocus step size. If your best HFR is around 1.0 then the first and last samples should be around 5.0 or so.

For determining filter offsets it's best to run the autofocus several times and take the average reading. Also move the scope between repeated autocus runs to avoid a certain star concentration possibly throwing the result off slightly.

Alan

@ollypenrice and @gorann If possible, could you post any RASA 8 image you have with a bright star in the frame, like Sadr or Alnitak, to give a comparison. A raw fits file would probably be best, with if possible, the star in different positions in the frame. Thanks. 😊

Some flaring is expected but it being so uneven on my images being angled towards the closest edge is what's rather annoying. I've sent my test images to FLO for them to assess.

Alan

Thanks for your replies Olly and Goran. Looking at previous images you've posted with the RASA it didn't look like you had this issue but I wanted to check before i pursue it further. it looks to be RASAs purchased in the past year or so having this problem, and it looks like Celestron are still having difficulty sourcing new mirrors. One person on CN had their RASA returned with the appearance that Celestron had gone over the mirror edge with a course file. It actually performed better like this though. 😲

I'll message FLO about it. I bought the last RASA they had in stock at the time a few weeks ago, though they have another one in stock now. It may well have the same issue though.

For RGB imaging it's not too big an issue stopping it down. At 200mm I was swamping the read noise by the sky background noise by a factor of 5 at 45s exposure at SQM 21.5, and masked to 180mm it takes around 1 min for the same figure. With a narrowband filter it will be more noticeable. With my FLT98 I have to expose RGB for 4 mins to swamp the read noise by a factor of 3.

Alan

The only difference between the two cables mentioned is the connector at the mount end of the cable. The NEQ6 along with many mounts has an RJ45 connector. The AZ-GTI though uses an RJ12 connector. These connectors are a different size, and number of pins, hence the two cables supplied by FLO.

If you want to use both mounts then you'll need one of each of the cables listed. It's possible to make an adapter cable between an RJ12 socket and RJ45 plug so that the AZ-GTI cable could work with the NEQ6, if you're experienced in working with RJ series connectors, but it would be a bit of a bodge and I wouldn't recommend it. 🙂

Alan

Can I ask if anybody with a Rasa 8 has excessive uneven flares on bright stars. This lengthy topic on CN shows similar issues, with Celestron acknowledging the problem but haven't yet fixed the problem on scopes returned, due to a lack of replacement mirrors. It seems to be an issue with the mirror edge finishing on some mirrors.

I did some tests using Lyra in various positions in the frame and I need an aperture mask of 180mm too fix the flares over most of the frame though the corners and extreme left and right still show it to some extent. I think an aperture mask of around 170mm or smaller is needed to fix them over the whole frame of an ASI2600.

This shows the problem using no mask and a 194mm mask. With 194mm only a small area near the centre is OK and this area increases with a smaller mask aperture. I used a simple cross shape cable routing to just give standard diffraction spikes to avoid a more curved routing possibly confusing the results.

I'd have thought that the best option is to fit a mask just in front of the mirror on those mirrors with the problem as only a few mm will then be lost which won't be a significant light loss.

On a side note I've made a chart showing the actual aperture as if it were a lens with the same exposed frontal area and the actual light loss with a frontal mask. I've wondered why the central obstruction is ignored when stating scope apertures. The 200mm Rasa  8 has a 94mm diameter central obstruction. If it had say a 190mm central obstruction would it still be classed an f2 scope as far as focal ratio is concerned even though it is of course not actually f2 aperture. 🤔

If it were a lens the Rasa 8 would not be f2 but around f2.26 or AV 2⅓. With the 180mm mask I'm currently using it's now f2.59 or AV 2¾. The focal ratio would be 2.2 though.

To have an AV of 2 or f2 the Rasa 8 needs a front plate diameter of 221mm with a 94mm obstruction.

A mask of 137mm would reduce the actual aperture by 2 stops to f4 though the focal ratio would be stated as 2.91 

Alan

The flat 2m USB3 ribbon type cable that comes with Zwo cameras is flexible and works, though is a little fragile if it gets repeatedly bent. Most cables are now made to USB3.1 standard with extra screening which makes them rather stiff. I have six of the Zwo cables so if you want one just paying for postage let me know. 😊

Alan

The AA269C specification gives typical framerates so any decent USB3 cable will work up to around 2m long. Longer than 2m, high quality cables like the Lindy would be preferable.

Quote

Approx. Max frame rates 8bit (assuming computer Bus operating at full bandwidth)*:

5280x3956    17.5fps    1x1 binning
2640x1978    17.5fps    2x2 binning
1760x1318    75fps    3x3 binning
584x440        210fps    9x9 binning

12bit mode:
Approx. 50% of above FPS.*

5280 x 3956 at 17.5 fps (8 bit) is an image data rate of 2.92 Gb/s

1760 x 1318 at 75 fps (8 bit) is 1.39 Gb/s

584 x 440 at 210 fps (8 bit) is 0.43 Gb/s

Alan

I think you're mixing up USB2 and USB3.

USB2 max rate = 480 Mb/s

USB3.0 max rate = 5 Gb/s

USB3.1 max rate = 10Gb/s

Your camera supports USB2 and USB3.0. Actually the USB3 interfaces have a USB2 interface built in so if you plug your camera cable which is USB3 into a USB2 port on your PC it will use the USB3's built in USB2 interface and give USB2 speeds.

Recent USB3 cables are made to USB3.1 spec so will support up to 10Gb/s though your camera will only work up to 5Gb/s. USB3.1 cables are fine being used as USB3.0.

As far as the maximum transfer speed you will actually get, these are usually significantly below the theoretical maximum. Using the Lindy cable you mentioned will give you the best chance at getting a fast speed. Get the shortest length USB3 cable you can get away with as that will improve your chances. Laptops and mini PCs are likely to give a lower speed than a desktop but you won't get a figure until you try it. 

My ASI178MM manages 30 f/s at max res of 3096 x 2080 while the ASI178MC manages 27 f/s with the GK Mini. Each frame is 3096 x 2080 x 8 bits which is 51.5Mb. At 30 f/s this is 1.5Gb/s and at 27 f/s this is 1.39Gb/s of image information.  There is an extra overhead for packing the data into the USB3 data blocks so likely around 2Gb/s actual data rate. Well below the 5Gb/s specified. 😉

Alan

3 hours ago, smr said:

Thanks. I'm not that brilliant at DIY stuff but if this is the only way to do it I'll have to give it a go. Is there anything obvious in the image above which might be contributing / causing it?

Focuser slop may cause it, where the focus tube can move slightly side to side. The easiest way to check is to take an image after a meridian flip and see if the elongated stars change position in the image. if they do change then it's likely the focuser tube moving side to side.

If there's no change then take another image with the camera rotated 90 degrees.  If there is again no change  then the camera is causing the tilt. If there is a change it's the imaging train before the camera.

I've found that the camera is almost always the cause and putting them on the test jig, (once you've made it 😀) enables you to fix it in 5 minutes during the day. Your camera has tilt adjustment so it should be fairly straightforward.

The wood frame box doesn't have to be fancy, just rigid enough that it doesn't move while the camera is rotated on top. The top and bottom of the box don't have to be exactly parallel to each other either for it to work.😊

Alan

It does look like a tilt issue. The right side corners look pretty reasonable while the left corners have elongated stars pointing generally inwards. This implies that the left side of the image, particularly the bottom left is closer than the optimum FF distance. Here's a CCD Inspector analysis

It's worth building a test jig as several others have done using pieces of wood and a cheap laser pen as shown here. Trying to adjust tilt by analysing star image tests is a never ending nightmare. If the camera doesn't have tilt adjustment then a tilt adjuster can be fitted in the image train before the camera, or the filter wheel if a mono camera, and the camera, filter wheel and tilt adjuster mounted together on the jig.

Alan

Are you using the latest version of EQAscom, version 200w from May 2021. I've installed Ascom & Eqmod on 3 Windows 11 64 bit mini PCs and they work fine. There was an issue initially, (can't remember what it was) which was solved with using the latest EQAscom.

Also what EQDirect cable chipset are you using. Look in Windows Device manager to check there's no yellow exclamation mark in its COM entry. FTDI chipsets are the ones to use nowadays. Prolific chipsets will work if they're genuine, but many cheap Prolific versions sold in the past were illegal clones which are now disabled by the drivers in Win 10 and 11. In Win 7 you could roll-back to older drivers which worked, but not using the latest drivers is made very difficult, if not impossible in later Windows versions.

The quickest way to access Device Manager in Win 11 is click on the Windows Start icon on the left of the task bar, and type 'Device Manager' It should show the Device Manager icon to click on, midway through typing. 🙂

Alan

On 21/07/2022 at 10:19, Uranium235 said:

No idea what went on in the bottom left, im pretty sure its either a flare, or a glint off something shiny.

That looks like a flare from Deneb. It's outside the sensor area but likely within the FOV of the scope. 🙂

Alan

35 minutes ago, Skipper Billy said:

I recently swapped the flat ribbon USB cable that came with an ASI178 for a Lindy Chromo and got an immediate 32% gain in max frame rate.

 

I forgot to mention in my first reply that it's worth 'ungrading' if the supplied cable is too long for your setup. Having the PC on the scope I use 1m or 0.5m cables which as well as being more tidy, may also allow a higher frame rate for planetary imaging.

The Zwo flat ribbon cables are only available in 2m lengths and with their construction have lower screening compared to the usual round USB3 cables where the data pairs are screened separately, and then the overall cable has another thicker screen. It's tempting to coil up the excess length but this will likely increase crosstalk between the data wires due to the low screening, leading to reduced performance . Try to route the excess in such a way that it isn't in contact with itself or other cables for any significant length.

I did enquire from FLO whether Zwo could supply 1m cables but FLO replied that they had already asked this question to Zwo but they said no. 

I'm using the Zwo flat USB3 on my RASA 8 as it's easier to route from the front camera but as it won't be used for planetary any loss in the frame rate isn't too important. 🙂

Alan

For a full frame sensor I'd say those stars are very good indeed. Being a posted jpg it's hard to say but the slight corner spikeyness is most likely very slight coma It's certainly better than my redcat which has noticeable coma in one corner on an APS-C sensor.

As you mentioned there is no required back focus distance with the redcat, the quoted figure just makes the distance scale on the focus ring read correct, but as long as you are able to go through focus you're fine. 😊

Alan

Hi Dave,

I found that the Lindy cables seem to have a firmer connection and require more efffort to plug and unplug, with less tendancy to move around compared to some generic cables, though this applied more to USB2 cables than USB3. If your current cable connection seems solid enough then there's no real need to 'upgrade'. The better cables have thicker wires for the two power pins compared to the data pins and more screening, so they are wider overall. Again this applied more to USB2 cables, than USB3  The various USB3 cable on Amazon etc. nowadays appear to have similar widths so electrically are likely very similar too.

Alan

Glad to hear you're happy with the results Tom. Odd that you're having trouble with the flats as I just use the light panel at full brightness with no paper sheets or ND filter, and end up with around 0.01 secs for LRGB and around 0.5 secs for narrowband. They all look good, and calibrate fine. The newer cameras don't have the short exposure issues that some earlier cameras did.

Hope you get around to contacting Atik at some time. 😉

Alan

Do you still have the unbinned files or did you bin them in the camera? If you don't have the unbinned files then you've removed the colour information by binning so it can't be resurrected again. 

Using super-pixel debayering on your unbinned raw files you will effectively bin the image 2x2 while keeping the colour information, and also avoid the normal debayer interpolation of every other pixel 

Alan

34 minutes ago, malc-c said:

EQDIR cables were originally intended for use with EQ mounts (hence their name).  Whilst it is possible to make one for a Dob, you have to be really careful that you don't end up frying the motor board (which as you know requires the replacement of the PIC micros).  The MC003 motor board has a 6 pin RJ11 socket, it only uses the four inner terminals, but with two shorted which go to the PICs RX and TX pins via two diodes and a few pull up resistors, with one pin connected to RA4 on both PICs, which can only be used as some form of trigger to manage the directional flow of serial signals, because otherwise with the TX and RX pins connected at the connector all that would happen if a FTDI 5v TTL serial adapter was connected would be an echo back to the PC of whatever is sent.

This was discussed on page 8 of the lengthy, but detailed thread repairing a blown motor board - Most of the board I've repaired have been down to people trying to connect their Dobs to a computer which results in popped diodes or burnt out UARTs in the PICs.

You can see this shorting of pins on the two images of the MC003 on that same page.  Top left of the first image below the silk screen R1 you can see the thick track linking the two.  This line is pulled high by R3, and then gets routed to the two PICs va D2 and D3 on the TX lines.

Now I'm not saying it's not possible to connect a Dob with an MC003 or MC004 board to a computer, but it's not something that has been in built by design, probably as an ALT/AZ mount is not one that someone would really use for imaging due to tracking and field rotation issues.  If you do manage to take an FTDI - 232- 5V cable and terminate it with an RJ11 and manage to get it to work without blowing the board then please let us know.  

Good point Malcolm.

I'm not sure what happens if you try to control an AZ-EQ6 in Azimuth mode using EQMod. The EQDirect page I linked to by the EQMod project does show the connections for an AZ-GTi. Whether EQMod can then control the AZ-GTi I don't know, but it's odd that it would be included if it doesn't.

In this rather old link, Chris Schillito, who wrote EQMod, says that  EQMod won't drive an AZ-EQ6 in Azimuth mode correctly, and GOTOs will be wrong. EQDirect is just a hardware interface for RS-232 level serial to TTL level serial communication so Alt-Az control is certainly possible using an EQDirect cable if suitable software is available.

Alan

The HEQ5 and AZEQ6 have an RJ45 on the mount for connecting either the Synscan controller or the EQDirect cable. The Synscan  to mount RJ45 to RJ45 is wired 1 to 1 so the details of the HEQ5/AZEQ6 EQDirect cable here giving the pinout of the mount RJ45 is also the pinout of the Synscan RJ45 connector.

Your Synscan RJ45 to Mount RJ12 cable likely has the colours of the wires used visible through the plugs so you can see which colour wires are used for the Synscan TX, RX and Gnd connections, and which pins they are connected to on the mount RJ12 plug. These would be the ones to use on your eqdirect cable for your Dob synscan system.

if the wire colours aren't visible on your synscan RJ45 to RJ12 cable then a multimeter continuity test can be used to check the pin connections. 🙂

Alan

Edit: The AZ-GTi has an RJ12 for the Synscan connection so this may be the same pinout as your Dob which the continuity check above can confirm.

Here's the Synscan pinout

This issue is mentioned in this previous thread. It seems Registax 6 must be installed before installing the update, which stops these errors happening. 🙂

Alan

Great images David despite the bit missing. The first two images are both labelled Hydrogen alpha though. 😊

Alan

43 minutes ago, Swoop1 said:

Thanks for the info Alan.

Not had this before on other lunar captures using the same rig. Could it be the altitude of the moon at the moment?

Being at low altitude, yes, it would be more red than if higher in the sky. On Sharpcap Image Controls-White Balance was the blue set to around 95 and the red around 45 which is what I use for a more neutral colour result. This is visible with 'debayer preview' on. It will autodetect the pattern (most likely RGGB) but can be overridden. The video is recorded as raw, (not debayered) to save using processor time doing debayering, which would impact the frame rate.

Autostakkert does the actual debayering during stacking, set by the Colour menu item. Auto detect is usually fine, though you can force other patterns or mono. I assume the Sharpcap preview and Autostakkert gave the same colour result (assuming you used debayer preview in Sharpcap).

Alan

Any update on your Apx60 Tom, and any reply from Atik?

Alan

This is fairly normal for OSC cameras. Whenever I do Moon images with OSC, in the capture program camera colour balance setting the red gain has to be reduced quite a bit and the blue gain turned up to near maximum to get a grey output. If you look at the response curve of your camera, red responds to a wider band of wavelengths compared to green and blue, and the blue output is significantly reduced as the QE is lower at the blue end compared to red.

Also if you look at the colour response of the moons reflected light, it's highest in red and way down in blue, so a pink moon is more realistic than the grey one our eyes are seeing, due to the brain making the predominant colour more neutral.

Alan

1 hour ago, 04Stefan07 said:

Is there a recommended laser to use in terms of power? I hear sometimes it can damage the camera sensor. I found a 650nm 1nW Red on ebay for cheap

I think you meant 1mW. 😉 A 1mW laser is fine, 5mW should be OK and 10mW is risky. When you get it check that it is 1mW. It will likely say 'Class II less than 5mW'. Class II is actually up to 1mW. I ordered a 1mW laser pen and it had Class III on it. Class III is up to 500mW though the pens were  likely 10mW by its brightness compared to another actual 1mW I also bought. ebay blocked some sellers who were selling Class III lasers as 1mW.

Alan